The present invention relates to a method for manufacturing a synthetic resin-made hollow member with an intermediate element incorporated therein, as well as an apparatus therefor, through the steps of previously incorporating the intermediate element such as a filter to between a pair of synthetic resin-made half bodies, and then bringing the two half bodies into abutment against each other and joining the two half bodies together at the abutted portion.
As the method for manufacturing a synthetic resin-made hollow member, there has conventionally been known, for example as shown in Japanese Patent Laid-Open Publication HEI 7-217755, a method employing a slide type injection molding technique (what is called die slide injection (DSI) molding). In this method, a pair of molding dies are provided, one molding die having one set of male molding portion and female molding portion for molding half bodies, and the other molding die having female molding portion and male molding portion opposed to those molding portions, where the one molding die is slidable relative to the other molding die in the direction in which the molding portions are arrayed. In this arrangement, after half bodies are simultaneously molded (primary injection), one molding die (slidable die) is slid relative to the other molding die (stationary die) so that the two half bodies left in the individual female molding portions are brought into abutment against each other, and then with the dies closed, molten resin is injected to peripheries of the abutted portion (secondary injection) so that the two half bodies are joined together.
This method employing the DSI technique is capable of enhancing the productivity to a great extent, as compared with the prior art in which the molding of half bodies and the abutment and joint of the half bodies would be done in separate processes. Still, the joint strength and the sealability of the abutted portion can be secured more stably than conventional cases in which half bodies would be joined together by bonding or thermal fusion processes.
It is to be noted that, in manufacturing a synthetic resin-made hollow member, the terms xe2x80x9cprimary injection (molding)xe2x80x9d herein refer to an injection (molding) step in which half bodies to form a hollow member (molded article) are molded by injecting molten resin (primary resin) into a cavity defined by closing molding dies together. Also, the terms xe2x80x9csecondary injectionxe2x80x9d refer to an injection step in which a pair of half bodies obtained by the primary injection (molding) step are joined together by bringing the pair of half bodies into abutment against each other and then injecting molten resin (secondary resin) to generally peripheries of the abutted portion.
Also for the manufacture of a synthetic resin-made hollow member with an intermediate element such as a filter incorporated inside, a high efficiency production using the DSI technique can be achieved, as disclosed in the aforementioned prior art publication, by performing the primary injection, then with the dies once opened, assembling a separately fabricated intermediate element to either one of half bodies, and thereafter, through die sliding and die closure processes, performing the secondary injection.
In this connection, in the DSI method, the position of the slidable die relative to the stationary die in the sliding direction naturally differs between before and after the sliding operation of the molding die (in other words, between primary injection and secondary injection). Therefore, particularly in the case of a multiple(e.g., 2)-yield molding apparatus capable of yielding a multiplicity (2) of molded articles simultaneously, the stationary die and the slidable die are both longer in length, so that a large eccentric load acts upon one or the other die closure, which makes the apparatus more prone to failures and the die-closing device more prone to eccentric wear. As a result, there has been a disadvantage of the method that the molding apparatus may incur shorter life or deterioration of the precision of molded articles.
In view of such problems, for example, Japanese Patent Laid-Open Publication HEI 9-76288 has proposed a so-called double DSI method in which sets of male molding portion and female molding portion as described above are provided in the stationary die in series in the die sliding direction, while slidable dies that operate independently of each other are provided in correspondence to the individual sets of molding portions.
According to this series type double DSI method, it becomes possible to make a uniform tightening load act upon the die closure, and besides since two slidable dies are provided separately from each other, the sliding amount of each slidable die can be made shorter, as compared with conventional counterpart (having one slidable die), so that the space can be saved.
When a synthetic resin-made hollow member with an intermediate element incorporated therein, such as a strainer with a filter incorporated therein, is manufactured by the DSI method, it has been conventional practice that after primary injection and before secondary injection, a separately fabricated intermediate element is assembled into either one of half bodies. In this case, however, there is a need of providing a step for manufacturing the intermediate element utterly separately from the steps for performing the molding and the abutting and joining of the half bodies, as well as a need of separately managing the intermediate element manufactured in this way as a part, which makes this method disadvantageous in cutting the manufacturing cost. Further, since the half bodies molded by the primary injection and the intermediate element manufactured separately are different in molding conditions as well as temperature and other conditions in the assembly, this method is disadvantageous also in attaining improvements in assemblability and assembly precision.
Also, when the intermediate element manufactured separately as described above is set to the half bodies, it would be conceived to provide an automatic assembler such as a robot outside the molding machine so that the intermediate-element incorporating step is automatized by assembling the intermediate element to the half bodies with this automatic assembler. For example, it is also possible to provide a holder (chuck) for clamping the intermediate element in a product takeout device (takeout robot) provided for use of taking products out of the injection molding machine, so that the intermediate element is clamped and traveled by this holder so as to be set to either one of the half bodies.
With the use of such an automatic assembler, in order to enhance the productivity by reducing the cycle time of production and to ensure a successful assembly precision, it is preferable that the distance for the intermediate element to be traveled is as short as possible.
Therefore, an object of the present invention is to provide a method, as well as an apparatus therefor, for manufacturing a synthetic resin-made hollow member with an intermediate element incorporated therein, the method being capable of molding hollow half bodies and an intermediate element and assembling them with the same dies, and yet the method involving a shorter travel of the intermediate element.
To achieve this object, in one aspect of the present invention, there is provided a method for manufacturing a synthetic resin-made hollow member with an intermediate element incorporated therein by, with the intermediate element placed between a pair of synthetic resin-made half bodies, bringing the half bodies into abutment against each other and joining the half bodies together at this abutted portion, the method comprising:
with use of a molding apparatus for slide type injection molding, the molding apparatus comprising: a stationary molding die having first and second hollow-member use stationary die portions in each of which a male molding portion and a female molding portion spaced from each other at a specified spacing are arrayed longitudinally, and a stationary-side intermediate-element use die portion placed between the two hollow-member use stationary die portions and having an intermediate-element molding portion; a movable molding die having first and second hollow-member use slidable die portions in each of which a male molding portion and a female molding portion spaced from each other at a specified spacing are arrayed longitudinally in an order reverse to that of the hollow-member use stationary die portions, and a movable-side intermediate-element use die portion placed between the two hollow-member use slidable die portions and having an intermediate-element molding portion; and intermediate-element moving mechanism, which has a moving arm driven by a motor, for moving an intermediate element molded by a combination of the stationary-side and movable-side intermediate-element use molding portions longitudinally up to a specified position, wherein the stationary and movable molding dies are openable and closable to each other and the first and second hollow-member use slidable die portions are slidable longitudinally at specified pitches, respectively, relative to the first and second hollow-member use stationary die portions, respectively, while the movable-side intermediate-element use die portion is non-slidable relative to the stationary-side intermediate-element use die portion,
a die closure step for performing die closure by closing the stationary molding die and the movable molding die to each other;
an injection step for, after the die closure step, injecting molten resin into a molding cavity defined by the two molding dies so that first and second half bodies for a current cycle are molded by combinations of the male molding portions and the female molding portions and that an intermediate element for the current cycle is molded by a combination of the intermediate-element molding portions, and further joining the first and second half bodies of a preceding cycle by injecting molten resin to an abutted portion between the first and second half bodies by a combination of the female molding portions;
a takeout step for, after the injection step, taking out a hollow member, in which the half bodies of the preceding cycle have been joined to each other with the intermediate element of the preceding cycle previously incorporated therein, while opening the molding dies; an intermediate-element assembly step for assembling the intermediate element for the current cycle to either one of the first and second half bodies for the current cycle by driving the intermediate-element moving mechanism and thereby moving the intermediate element; and a sliding step for sliding the first and second hollow-member use slidable die portions to specified pitches, respectively, longitudinally in a direction reverse to that of the preceding cycle,
these steps being iteratively performed, whereby a hollow member in which the first and second half bodies have been joined to each other with the intermediate element previously incorporated between the two half bodies is obtained at each one-time opening and closing operation of the stationary molding die and the movable molding die.
In another aspect of the present invention, there is provided an apparatus for manufacturing a synthetic resin-made hollow member with an intermediate element incorporated therein by, with the intermediate element placed between a pair of synthetic resin-made half bodies, bringing the half bodies into abutment against each other and joining the half bodies together at this abutted portion, the apparatus comprising:
first and second hollow-member use stationary die portions in each of which a male molding portion and a female molding portion spaced from each other at a specified spacing are arrayed longitudinally;
a stationary-side intermediate-element use die portion placed between the two hollow-member use stationary die portions and having an intermediate-element molding portion;
first and second hollow-member use slidable die portions in each of which a male molding portion and a female molding portion spaced from each other at a specified spacing are arrayed longitudinally in an order reverse to that of the hollow-member use stationary die portions;
a movable-side intermediate-element use die portion placed between the two hollow-member use slidable die portions and having an intermediate-element molding portion;
opening and closing hydraulic mechanism for opening and closing a movable molding die having the first and second hollow-member use slidable die portions and the movable-side intermediate-element use die portion, relative to a stationary molding die having the first and second hollow-member use stationary die portions and the stationary-side intermediate-element use die portion;
sliding mechanism which has driving cylinders for, while holding the movable-side intermediate-element use die portion non-slidable, sliding the two hollow-member use slidable die portions longitudinally at specified pitches, respectively, relative to their corresponding hollow-member use stationary die portions;
intermediate-element moving mechanism, which has a moving arm driven by a motor, for moving an intermediate element molded by a combination of the stationary-side and movable-side intermediate-element use molding portions longitudinally up to a specified position; and
injection mechanism, which has a injection molding machine, for injecting molten resin into a molding cavity defined by closing the stationary molding die and the movable molding die to each other;
wherein the apparatus performs an injection molding process in which for each one-time opening and closing operation of the stationary molding die and the movable molding die, the hollow-member use slidable die portions slide at specified pitches, respectively, relative to their corresponding hollow-member use stationary die portions while the intermediate-element moving mechanism moves the molded intermediate element to a specified position, so that first and second half bodies for a current cycle are molded by combinations between male molding portions and female molding portions of the first hollow-member use stationary die portion and the first hollow-member use slidable die portion, and that an intermediate element for the current cycle is molded by a combination of the intermediate-element molding portions of the stationary-side and movable-side intermediate-element use die portions, and further that the first and second half bodies of the preceding cycle are joined together by injecting molten resin into an abutted portion between the first and second half bodies by a combination between the female molding portions of the second hollow-member use stationary die portion and the second hollow-member use slidable die portion, whereby a hollow member in which the first and second half bodies have been joined to each other with the intermediate element previously incorporated between the half bodies is obtained at each one-time opening and closing operation of the stationary molding die and the movable molding die.
In the above mentioned aspects of the present invention, it is preferable that an initial position of the intermediate-element moving mechanism for moving the intermediate element is set to the stationary-side or movable-side intermediate-element use die portion.
According to the present invention, at each one-time opening and closing operation of the stationary molding die and the movable molding die, a hollow member in which first and second half bodies have been joined to each other with an intermediate element previously incorporated between the two half bodies can be obtained.
In this case, since the step of fabricating the intermediate element can be performed as a sequence of steps together with the molding step and abutting and joining step of the half bodies, it is no longer necessary to separately manage the intermediate element as a component part as would be done in the prior art. Further, since the intermediate element and the half bodies are generally similar in molding conditions and assembling temperature condition to each other, it becomes possible to improve the assemblability and the assembly precision.
Also, by virtue of the provision of the intermediate-element moving mechanism for moving the molded intermediate element longitudinally up to a specified position, the intermediate element can be automatically assembled to a half body, allowing not only the improvement in assembly precision but also saving of labor and improvement in production efficiency to be achieved.
Further, by virtue of the provision of the intermediate-element moving mechanism in the molding die, the travel of the intermediate element can be shortened, as compared with the case where an automatic assembler provided outside the molding apparatus is used, so that the assembly precision of the intermediate element to the half body can be even further enhanced and besides that the production cycle time can be further reduced.
Still further, according to the present invention, since the initial position of the intermediate-element moving mechanism for moving the intermediate element is preferably set to an intermediate-element use die portion on the stationary side or the movable side, the travel of the intermediate-element moving mechanism required to move the intermediate element can be even further shortened so that the assembly precision can be even more improved and that the production cycle time can be even further reduced.